1. Field of the Invention
The present invention relates to an apparatus and a method for providing a passage in a sealing member of a container of a fluid sample, the passage being intended to allow the withdrawal of at least a portion of the fluid sample from the container, the latter being also referred to in the following as sample container. The invention also relates to a sleeve to be stuck or pierced through a sealing member of a sample container, whereby the sleeve --after having been inserted into the sealing member--defines said passage. Accordingly, the sleeve serves as a kind of cannula.
The sealing member may be a stopper consisting of an elastic deformable material, for instance of a rubber elastic material. The stopper may consist for instance of natural rubber and/or a synthetic plastic rubber such as silicon caoutchouc, polyisoprene or another more or less rubber elastic polymer such as a relatively elastic polyurethane. The stopper may also consist of another suitable, deformable material such as cork.
The sealing member, however, may also be a cap such as a screw cap. The screw cap may comprise a screw member having a central section provided with a through-going axial hole and a ring or tubular section provided with an inner thread screwed onto an outer thread of the sample container. The axial hole may then be closed by a covering foil applied to the outer, upper side or possibly on the inner, lower side of the screw member. The screw member may consist of a polymer to some extent elastically deformable but not as elastic as rubber. The screw member may consist for instance of a thermoplastic polymer such as polypropylene, polyethylene, polystyrene or relatively hard polyurethane. The foil may consist of a metallic material or possibly of one of the aforementioned thermoplastic polymers. The screw cap, however, may consist of a single piece including screw member and foil. The throughgoing hole could then be replaced by a blind hole bounded at one end by the foil, so that the foil will be constituted by a portion of said single piece, which may then have one of the aforementioned polymers as screw member material.
Normally, the fluid sample is at least in part and/or at least substantially liquid. More specifically, the fluid constituting the sample may comprise a body fluid, such as blood or blood serum or urine of a living human being or an animal. Accordingly, the sample may comprise a liquid containing dispersed solid particles and possibly dissolved gas, or fluid completely liquid.
The body fluid to be analyzed may have been introduced into the sample container in one of various ways before the sealing member has been provided with the sleeve defining said passage. If the sealing member consists of a stopper more or less rubber elastic, the body fluid may have been introduced into the sample container, for instance, by first producing a vacuum inside the container and then sticking a thin, needle-like cannula through the sealing member, to have the vacuum suck the fluid into the container through the cannula. After the fluid has been sucked into the container, the cannula is withdrawn from the sealing member, i.e. the stopper. The elasticity of the latter causes then the hole created before by the cannula to be closed so that the container now containing a body fluid will again be tightly sealed by the sealing member.
In case the sealing member is realized as screw cap, the body fluid may have been brought into the sample container while the latter was open. If the fluid has been introduced into the sample container, the latter will have been closed, of course, by means of the cap.
After the sealing member has been provided with a sleeve for creating the passage, the fluid sample or part thereof may be extracted from the container by means of a suction device comprising a fluid conduit, such as a hose, introduced into the passage. The extracted fluid may then be analyzed. Or, several portions of the fluid sample may be extracted, one after the other, and subjected to various procedures of analysis.
2. Description of the Prior Art
Relatively weak hoses are normally used as fluid conduits for sucking liquid fluid out of sample containers. Such hoses cannot be pushed directly through stoppers which consist of one of the previously specified materials, and are relatively thick. One could of course remove the stopper to make the fluid sample in the container accessible. This method, however, even though frequently used, has several drawbacks. There is the risk, for example, that a layer of the sample will adhere to the extracted stopper. The container usually consists of a thin-walled test glass tube and the stopper is firmly seated in the glass tube and additionally held in place by the partial vacuum created temporarily inside the tube while the stopper is displaced for opening the container. Therefore, the removal of the stopper generally requires considerable force and carries the risk that the air streaming abruptly into the container at the moment of stopper extraction will produce an aerosol mist comprising fine droplets of the liquid fluid. This and/or any possibly occuring jerk of the sample container may spray and/or spout droplets and/or drops out of the glass tube. The latter may even possibly break. If sample liquid adheres to the stopper or comes out of the sample container in any one of the other aforementioned ways, such liquid may contaminate devices and/or persons and cause serious dangers of infecting the concerned persons. Furthermore the removal of a stopper is relatively time-consuming and is--particular in consideration of the previously mentioned drawbacks--not easily feasible with an apparatus working fully automatically. Similar problems and disadvantages could arise by removing a sealing member consisting of a screw cap from a sample container.
Devices and methods for providing a passage in a stopper of a container of a fluid sample, the passage being intended to allow the withdrawal of the sample, without removing the stopper have been known, however, in the art. A device and a method of this kind are disclosed for example in the international patent disclosure publication WO87/05208 as comprising a sleeve designated as cannula and including a pipe bounded at one end by an oblique curved surface so as to form a prong. The other end of the pipe merges with a seating for receiving a collecting vessel of a suction device. For sucking the liquid sample out of the container, the prong of the sleeve or cannula is stuck through the stopper. Subsequently, the suction hose of the suction device is stuck through the pipe. However, the asymmetric shape of the prong of the pipe has the effect, that the pipe will tend to deviate from the axis of the stopper when it is stuck into the latter so that the sleeve or cannula and its seating will not get properly positioned. This deflection will be of particular disadvantage if the insertion of the sleeve or cannula is to be performed automatically, by mechanical means and without manual aid. Even though claim is made in the cited publication that the particular shape of the pipe prong will avoid or at least greatly reduce the risk of cutting pieces off the stopper, considerable danger still remains, that the hollow pipe with its sharp end will act like a hollow punching tool and will cut particles off the stopper. This is particularly likely to occur at the rear end of the oblique surface forming the prong. Particles cut off the stopper may then fall into the sample liquid while the pipe penetrates through the stopper and/or if the suction hose is pushed through the pipe, thus hindering the suction of the liquid sample and/or the analysis of the sample performed subsequently.